1. Field of the Invention
This invention relates to dental mirrors and, more particularly, to dental mirrors comprising a reversible mirror having two reflective surfaces.
2. Description of the Prior Art
Dental mirrors of the prior art comprise a relatively thin circular glass element having a smooth, planar surface on the top of the glass element, and a reflective coating on the bottom of the glass element. The outer edge of the element is ground. The glass element is typically inserted into a metal or a plastic socket. The socket includes an edge which is crimped around the outer periphery of the mirror at the ground area to hold or retain the glass mirror element in the socket. The ground area is an area which slopes away from the mirror surface to allow the crimped portion of the socket to firmly grasp the mirror element.
The ground area of the glass, where the glass is held into a socket, is not smooth, does not comprise a smooth, planar surface, and accordingly is pitted. The pitted sloping side accordingly collects dirt, debris, and blood, which are very difficult to remove by ordinary cleaning processes. Germs from a patient's mouth which get onto the ground area of the mirror may become deeply imbedded into the pitted area and accordingly may survive autoclave sterilization.
When the top or upper surface of the glass is scratched, the entire mirror apparatus is unusable and is accordingly thrown away. This represents an economic loss, since the mirror cannot be reversed so as to use the other side.
With the reflective or mirror coating on the bottom surface of the glass, the mirror is referred to as a plane surface mirror. The reflection in the mirror is through the glass, which represents a substantial distance, typically at least sixty thousandths of an inch, that the dentist is viewing from, or through, as he uses the mirror. That is, the closest that the dentist can get with a mirror to a tooth is at least the thickness of the glass mirror element.
Furthermore, there are occasions when it is desirable for a dentist to view in opposite directions substantially simultaneously. For doing so, a double surface mirror would be advantageous. With the mirror apparatus of the prior art, the glass element alone comprises the mirror, and accordingly the apparatus must be reversed and repositioned in order to allow viewing in opposite directions. A more desirable situation is a front surface mirror, with the reflective surface no more than ten or fifteen thousandths of an inch from the surface of the element.
There are two types of handles used with prior art dental mirrors, one of which is metal and one of which is plastic. The plastic handled apparatus is preferred for cost purposes since the cost of such plastic handles is less than the cost of metal handles. However, the metal mirror handles are preferred for endodontic testing purposes. That is, with the heavier, more dense metal handles, a dentist may reverse the mirror and use the handle of the mirror as an endodontic tool. The lighter, less dense plastic handle cannot be used in such a manner.
The above paragraphs generally discuss a typical dental mirror of the prior art and some of its shortcomings. In addition to the general description given above, the prior art also includes several patents. One such patent is U.S. Pat. No. 3,300,859, which discloses a pair of glass mirror elements to produce a double mirror. However, both mirrors comprise plane surface mirrors and the reflection in each mirror is viewed through the thickness of its glass element. A frame, having arcuate indentations, is fixed to the mirror elements, and the mirror elements cannot be reversed when one becomes scratched.
U.S. Pat. No. 3,539,247 discloses a dental mirror including a housing having a reflective element which includes a belt or film which may be changed or cleaned by rolling an adjacent portion of the belt or film to take the place of the original portion. A reflective surface is disposed beneath the belt or film. A wetting agent is disposed within the housing, and sealing members are used to prevent the wetting agent from leaking out of the housing and to act as a squeegee as the film or belt is rolled.
U.S. Pat. No. 3,638,013 discloses a combination light and mirror apparatus in which fiber optics are used to transmit light to a dental mirror. For the mirror, a glass element is used, in one embodiment, and plastic, such as lucite, is used in another embodiment. However, all of the mirror elements include reflective surfaces remote from the planar mirror surfaces, typical of the prior art.
U.S. Pat. No. 3,829,199 discloses disposable dental mirror apparatus, which includes a removable mirror element secured to a handle. The mirror element includes only a single reflective coating disposed on the bottom of a plastic disc, and the disc is secured within a base. The disc and base comprise the disposable portion of the dental mirror apparatus.
U.S. Pat. No. 3,468,030 discloses a triangular shaped flexible mouth prop which fits into the mouth between the cheek and the teeth to block the parotid gland. The apparatus includes absorbent material on one side and a foil strip on the other side for reflecting light.